The present invention relates to polyether/polycarbonate block copolymers and to a process for their production.
Polycarbonates are well-known commercially available resinous materials having a variety of applications. Polycarbonates are typically prepared by the reaction of dihydroxy compounds and a carbonate precursor, such as phosgene and aromatic dicarboxylic acid dihalides. Polycarbonates are high temperature, high performance thermoplastic engineering polymers with a combination of good thermal and good mechanical properties, particularly if the polycarbonate has been prepared from an aromatic diol. Known polycarbonates are, however, unsuitable for applications where hydrolytic stability and solvent resistance are required.
Attempts have therefore been made to modify the known polycarbonates in a manner such that the advantageous thermal and mechanical properties are retained but the problems of lack of hydrolytic stability and lack of adequate solvent resistance are overcome. Because polycarbonates are generally incompatible with other resinous materials, one approach to resolving this problem has been to polymerize non-polycarbonate resinous materials into the polycarbonate molecule to produce a block copolymer. Condensation block copolymers are normally synthesized as shown below: ##STR4## Either two telechelic oligomers are coupled, or monomers are polymerized in the presence of a telechelic oligomer (see, for example, McGrath et al Poly. Eng. Sci. 1977, 17, 648). Another approach is disclosed in Published European Patent Application 353,478. More specifically, European Application 353,478 discloses a process for making poly(aryl ether/thioether)poly(aryl carbonate) block copolymers in which a portion of the poly(aryl ether/thioether) blocks are joined to the poly (aryl carbonate) blocks through an ether oxygen or thioether sulfur atom.
The copolymers produced in accordance with European Patent Application 353,478 do not, however, have a predictable block length and require reaction times such that the reaction can not be carried out in an extruder. These copolymers would not therefore be suitable for in situ compatibilization of a polymer blend in processing equipment such as extruders or for applications which require block copolymers having long polyether segments.